Conventional data or information storage systems typically implement a file system to logically organize the information as a hierarchical structure of directories and files on a storage device.
The storage devices are typically disk drives organized as a disk array, wherein each disk is a self-contained rotating magnetic media storage device. The term disk in this context is synonymous with, for instance, a hard disk drive (HDD), a direct access storage device (DASD) or a logical unit number (LUN) in a storage device. Unless the context indicates otherwise, the term “disk” as used herein is intended to embrace not only magnetic storage devices, but also optical, solid state and other types of storage devices.
Recently, Network Attached Storage (NAS) and Storage Area Network (SAN) technologies have been used to provide storage with greater capacity, higher reliability, and improved availability. SAN is an architecture to attach remote storage devices to servers in such a way that the storage devices appear as locally attached to the operating system. NAS, in contrast to SAN, uses file-based protocols where it is clear that the storage devices are remote.
Data security is an important consideration in storage systems. One component of ensuring data security is generating backup copies of information stored on physical media in the storage system. Traditional techniques for generating backup copies of information stored on physical media involved making a redundant copy of the information, usually on a separate storage medium such as, e.g., a magnetic tape or optical disk. Such techniques raise multiple issues in large capacity storage, high availability storage systems. Foremost, traditional backup procedures may render the storage system inaccessible during the backup process, which is inconsistent with the goal of maintaining high availability. In addition, traditional backup procedures consume significant storage space, much of which may be wasted.